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					         Fun Physics You Can See
           Lasers, Holograms and Spectroscopy




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      The Inside Scoop on Light




•Light is a wave, kind of like a wave in the ocean

•These light waves carry energy. This energy can do many interesting
things, like help grow a plant, produce electric currents, or cause
chemical reactions.

•Light carries a different amount of energy depending on its wavelength.
Wavelength: the Secret to the Rainbow
• Light that has a longer
  wavelength appears more red,
  and light that has a shorter
  wavelength appears blue.

• The shorter the wavelength,
  the higher the energy carried
  by the wave.

• You may have heard of
  “ultraviolet” or “infrared” light.
  That is light at either extreme
  of wavelength, very short
  (ultraviolet) or very long
  (infrared).

• Our eyes cannot always detect
  light if the wavelength is very
  long or very short.
Diffraction Gratings:
The Bending of Light
        • A wave is bent when it hits a rough
          surface or passes through a small
          opening, or aperture. This is called
          diffraction. Diffraction happens to
          all types of waves, including light.

        • The white light we see from the sun
          and light bulbs is not really white. It
          is made up of many different colors.
          These colors that make up the light
          are known as a spectrum. If you
          have ever seen a rainbow, then you
          have seen the visible spectrum.

        • Diffraction gratings separate light
          into the different colors of light that
          it is made of.
             Spectroscopy:
      The Finger Prints of Elements
                •Spectroscopy is the
                study of the spectrum
                from different atoms
                and molecules.

• Electrons in an atom can get
  excited. An excited electron is
  in a state of high energy.
  Sometimes these electrons
  jump down to a state with low
  energy. The difference in
  energy is given off as light.

• Since different kinds of light
  have slightly different spectra,
  scientists can use a star's
  spectrum to figure out what
  elements it is made of.
Phosphorescence: A Big Word for
       Glow-In-the-Dark
 Certain compounds contain things called phosphors.
                         •Phosphors emit visible light when
                         exposed to energy, like from ultraviolet
                         light. They do this because of electrons
                         jumping between energy states.
                         •In order to give the electrons enough
                         energy, you have to use light with a
                         short wavelength.


•Some phosphors, like the
ones in fluorescent lights,
do not glow after the energy
source is taken away. Those
that continue to glow after
the energy is taken away are
called phosphorescent.
            Light Can Carry a Lot of
                  Information




• Holograms and fiber optics are two methods of information transfer
  that use light.

• Holograms are made using lasers to record a 3 dimensional object
  on a 2 dimensional surface, like a piece of paper. Our eyes see the
  object because of controlled use of diffraction.

• Fiber optics is a method of sending information as light through a
  cable. This light signal can be changed to music, video and more!
                       Fun Facts
• A hologram the size of a sugar
  cube could hold enough
  information for about 30 DVD
  movies!
• CD’s, like holograms, use
  diffraction patterns to store
  information.
• Light from the sun can be
  transformed into usable energy
  to power homes, cars and
  more.
• Light at the far ends of the
  spectrum, like microwaves
  (far into the infrared) and
  gamma rays (far into the
  ultraviolet) have some very
  interesting properties. You
  could read about them in the
  library, or on the internet!

				
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posted:10/6/2012
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